Surgery necessarily severs blood vessels, thereby releasing blood into the incision. Bleeding during surgery may cause several undesirable results. Blood covering critical areas of the patient's anatomy increases the risk of error and the time required for operations by obscuring the surgeon's field of vision. Additionally, blood loss may directly threaten the patient's life during the surgery, making transfusions necessary. However, transfused blood is drawn from a limited supply and may expose the patient to communicable diseases. Finally, compensating for blood loss also requires additional time and energy from both patient and medical facility during the patient's recuperation after surgery. Thus, the cessation of bleeding, known as hemostasis, is highly desirable.
Hemostasis is facilitated by coagulation, a process whereby blood is converted from a liquid to a solid state. Coagulation may be effected by passing an electric current through the body of the patient so that concentrated electrical energy heats the tissue in contact with the coagulation electrode. Thus, in monopolar electrosurgery a radio frequency current is passed from an active electrode, where the current is highly concentrated, through the patient to a dispersive electrode. The current is diffuse at the dispersive electrode, so coagulation occurs only near the active electrode. Various frequencies are used, but frequencies above 400 Khz are commonly employed.
Desiccation coagulation may be achieved by using a blunt active electrode and relatively low power. The power required varies with the conductivity of the tissue and the area of contact between the tissue and the active electrode, but voltages in the range from 200 V to 900 V are typical. The current raises tissue temperature enough to dry and shrink cells, denature protein, and promote clotting of blood.
Fulguration coagulation, by contrast, employs either a blunt or fine electrode and relatively high power, voltages in the range 900 V to 2000 V being typical. The active electrode is maintained at a small distance from the tissue so that sparks jump the gap from the active electrode to the tissue. At each point of the tissue contacted by a spark, the current density is quite high, so the tissue at the contact point is seared. However, the surface area seared by each spark is small, and the overall heat damage to the tissue is shallow. Fulguration usually provides good cosmetic results after healing.
If proper distribution of current is not maintained during coagulation, the overall heat damage to the patient may be excessive. Undesirable current concentration due to contact between the active electrode and the tissue is exacerbated by the tendency of some bare metal electrodes to stick to tissue. When an electrode sticks to tissue, much or all of the electrical current discharged from the electrode may pass through the same portion of the patient's body. The resulting burns may substantially increase the patient's healing period. In addition, of course, tissue is damaged when a sticking electrode is pulled away from the tissue.
Electrodes are also used to destroy undesirable tissue by electrothermal ablation. Ablation involves the thermal destruction of undesirable tissue. For instance, endometrial tissue proliferating outside the uterus in a woman's pelvic or abdominal cavity may impair fertility. An electrode carrying high frequency current can be passed over such tissues to destroy the abnormal cells. Ablation typically employs lower voltages and higher currents than electrosurgical coagulation. During ablation, unlike fulguration, sparking is unnecessary or even undesirable. As with coagulation, however, it is desirable during ablation to apply the current at evenly-distributed concentration points.
The term "diathermy" encompasses not only ablation and electrosurgical coagulation, but also certain medical procedures used in treating arthritis or rheumatism. As used herein, however, diathermy means the application of high frequency electrical current to tissue to perform coagulation, ablation, or both. Proper current distribution for diathermy requires that fulguration sparks or other current concentrations be distributed over a plurality of discrete tissue locations. Devices previously known, however, emit sparks from one electrical discharge point or non-uniformly over a region. Because each spark or point concentration coagulates or ablates only a small surface area, larger areas can be difficult to treat, even if the active electrode is moved slightly after each discharge. Maintaining a spark gap for fulguration is difficult because tissue surfaces requiring coagulation are not often planar, are often located within incisions that restrict the surgeon's freedom of movement, and may be difficult to view.
Advantageously, a proper current distribution may be maintained using the present invention simply by placing the active electrode against the tissue and rolling the active electrode along the tissue. As the active electrode rotates, successive pluralities of electrical discharge points situated on the rotating active electrode come into spark gap distance or contact with the tissue. The surgeon's task in maintaining a spark gap becomes the manageable one of maintaining contact between the active electrode and the tissue, rather than the difficult task of maintaining a consistent distance between the active electrode and the tissue or covering a large area with a few discharge points.
Prior art devices are also monopolar in nature. That is, the surgeon manipulates a small active electrode which emits current that travels through the patient to a large dispersive electrode, and thence back to the electrosurgical generator. The dispersive electrode, also denoted the return electrode or return lead, is conventionally large and fixed in place on the patient's leg or some other location permitting large surface area contact between the return lead and the patient.
A major drawback of such monopolar systems is that the electrical current entering the patient from the active electrode is not always constrained to exit the patient at the return lead. Accidental contacts between the surgeon and patient or between the patient and some conductive operating fixture such as a table may result in burns to patient or surgeon or both when the electrical current deviates from its preferred path back to the electrosurgical generator through the dispersive electrode.
Thus, it would be an advancement in the art to provide an active electrode capable of discharging electric current in a substantially uniform distribution.
It would also be an advancement in the art to provide an active electrode for diathermy that did not easily stick to tissue.
It would be a further advancement to provide a diathermy apparatus and method for uniformly and rapidly coagulating or ablating an area of tissue substantially larger than the area affected by any single spark.
It would be an additional advancement in the art to provide a bipolar diathermy apparatus and method in which the return electrode traveled along the patient's tissue in close physical and electrical proximity to the active electrode, thereby reducing the risk of burns by more tightly constraining the paths current may take.
Such a diathermy apparatus and method are disclosed and claimed herein.